Prenatal and pre-weaning growth and nutrition of cattle: long-term consequences for beef production

Consequences of prenatal and preweaning growth for feedlot growth, intake and efficiency of Piedmontese- and Wagyu-sired cattle

Consequences of low (mean 28.0 kg, n = 77) and high (mean 38.4 kg, n = 77) birthweight followed by slow (mean 548 g/day, n = 75) or rapid (mean 859 g/day, n = 79) growth to weaning for feedlot growth, intake and efficiency from 26 to 30 months of age were determined in Wagyu × Hereford (n = 81) and Piedmontese × Hereford (n = 73) cattle. Cattle were selected for study based on birthweight and preweaning growth rate, from multi-modal distributions achieved by imposition of low or high maternal nutrition during pregnancy and lactation, with the objective of achieving as close as possible to a 30% difference in birthweight and a 2-fold difference in preweaning growth rate between progeny groups. High birthweight cattle entered the intake test 57 kg heavier, grew 100 g/day more rapidly, and ate 1.0 kg dry matter /day more than the low birthweight cattle. The high birthweight cattle tended to have a higher feed conversion ratio than low birthweight cattle, but net feed intake did not differ due to birthweight group. Cattle grown rapidly to weaning entered the intake test 29 kg heavier, grew at an equivalent rate, and ate 0.7 kg dry matter/day more than the cattle grown slowly to weaning. No differences in feed conversion ratio or net feed intake were observed between the preweaning groups. When assessed at the same liveweight, differences in dry matter intake and/or feed conversion ratio due to birthweight or preweaning growth were no longer apparent. Interactions between prenatal and preweaning growth, or between sire genotype and early-life growth, were not evident for feedlot growth, intake or efficiency. It is concluded that severely restricted growth during prenatal life or from birth to weaning results in cattle that are smaller and consume less feed at the same age as their well grown counterparts; however, long-term effects of growth during early life on efficiency of utilisation of feed are not evident.

Performance of steer progeny of sires differing in genetic potential for fatness and meat yield following postweaning growth at different rates. 2. Carcass traits

The steer progeny of sires genetically diverse for fatness and meat yield were grown at different rates from weaning to feedlot entry and effects on growth, carcass and meat-quality traits were examined. The present paper, the second of a series, reports the effects of genetic and growth treatments on carcass traits. A total of 43 sires, within three ‘carcass class’ categories, defined as high potential for meat yield, marbling or both traits, was used. Where available, estimated breeding values for the carcass traits of retail beef yield (RBY%) and intramuscular fat (IMF%) were used in selection of the sires, which were drawn from Angus, Charolais, Limousin, Black Wagyu and Red Wagyu breeds, to provide a range of carcass sire types across the three carcass classes. Steer progeny of Hereford dams were grown at either conventional (slow: ~0.5 kg/day) or accelerated (fast: ~0.7 kg/day) rates from weaning to feedlot entry weight, with group means of ~400 kg. Accelerated and conventionally grown groups from successive calvings were managed to enter the feedlot at similar mean feedlot entry weights at the same time for the 100-day finish under identical conditions. Faster-backgrounded groups had greater fat levels in the carcass than did slower-backgrounded groups. Dressing percentages and fat colour were unaffected by growth treatment, whereas differences in ossification score and meat colour were explained by age at slaughter. There were significant effects of sire type for virtually all carcass traits measured in the progeny. Differences in hot standard carcass weight showed a clear advantage to European types, with variable outcomes for the Angus and Wagyu progeny. Sire selection by estimated breeding values (within the Angus breed) for yield and/or fat traits resulted in expected differences in the progeny for those traits. There were large differences in both meat yield and fatness among the types of greatest divergence in genetic potential for those traits, with the Black Wagyu and the Angus IMF clearly superior for IMF%, and the European types for RBY%. The Angus IMF progeny performed as well as that of the Black Wagyu for all fatness traits. Differences in RBY% among types were generally reflected by similar differences in eye muscle area. Results here provide guidelines for selecting sire types to target carcass traits for specific markets. The absence of interactions between growth and genetic treatments ensures that consistent responses can be expected across varying management and production systems.

Economic effects of nutritional constraints early in life of cattle

An experiment was conducted at the Grafton Agricultural Research Station on the northern coast of New South Wales whereby low and high pasture nutritional systems were imposed on a herd of Hereford cows during pregnancy and from birth to weaning in a factorial design. Offspring representing extremes of growth to birth and/or weaning were then selected for study of long-term consequences of growth early in life. Implications of the nutritional treatments of cows on subsequent weaning rates were also tested with data from previous studies. The extent to which these extreme maternal nutritional and offspring growth scenarios affected herd profitability was tested with the Beef-N-Omics decision support package. For the representative cattle enterprise modelled, gross margin per hectare ranged from $A114 to $A132. In all cases, the gross margin for those groups with fetal growth based on a higher level of nutrition exceeded that of their peers on a lower level of nutrition. It is more profitable for cows and calves to have access to a high standard of nutrition during pregnancy and up to weaning than for them to have access only to a poor standard of nutrition. Incorporating differential weaning rates following maternal nutritional treatments reduced gross margins per hectare by up to 30%. On average, a 1% reduction in weaning rate resulted in a 4.5% reduction in gross margin. Restricted cow–calf nutrition affects the future cow fertility, as well as the current calf progeny, economically.

Consequences of prenatal and preweaning growth for yield of beef primal cuts from 30-month-old Piedmontese- and Wagyu-sired cattle

Cattle sired by Piedmontese or Wagyu bulls were bred and grown within pasture-based nutritional systems followed by feedlot finishing. Effects of low (mean 28.6 kg, n = 120) and high (38.8 kg, n = 120) birthweight followed by slow (mean 554 g/day, n = 119) or rapid (875 g/day, n = 121) growth to weaning on beef primal cut weights at ~30 months of age were examined. Cattle of low birthweight or grown slowly to weaning had smaller primal cuts at 30 months as a result of reduced liveweight and smaller carcasses compared with their high birthweight or rapidly grown counterparts. Hence they require additional nutritional and economic inputs to reach target market weights. At equivalent carcass weights (380 kg), cattle restricted in growth from birth to weaning yielded slightly more beef and were somewhat leaner than their rapidly grown counterparts, resulting in primal cuts being up to 4% heavier in the slowly grown compared with the rapidly grown cattle. Compositional differences due to birthweight were less apparent at the same carcass weight, although low birthweight cattle had a slightly (~2%) heavier forequarter and slightly lower (~1%) hindquarter retail yield, and less shin-shank meat (~2%) than high birthweight cattle, suggesting only minor effects on carcass tissue distribution. There were few interactions between sire genotype and birthweight or preweaning growth, and interactions between birthweight and preweaning growth were not evident for any variables. However, variability between cohorts in their long-term responses to growth early in life suggests other environmental factors during early-life and/or subsequent growth influenced carcass yield characteristics. Overall, this study shows that effects of birthweight and preweaning growth rate on carcass compositional and yield characteristics were mostly explained by variation in carcass weight and, hence, in whole body growth to 30 months of age.

Performance of steer progeny of sires differing in genetic potential for fatness and meat yield following post-weaning growth at different rates. 1. Growth and live-animal composition

The present experiment, ‘Regional Combinations’, examined growth, and carcass- and meat-quality traits in the progeny of sires genetically diverse for fatness and meat yield when grown at different rates from weaning to feedlot entry. The present paper is the first of several papers describing results from the New South Wales site, one of four in the project. It reports the effects on growth and body composition of steers during backgrounding and feedlot finishing phases. A total of 43 sires within three carcass-class categories, defined as high potential for meat yield, for marbling or for both traits, was used, based on estimated breeding values for retail beef yield and intramuscular fat. Sires were drawn from Angus, Charolais, Limousin, Black Wagyu and Red Wagyu breeds, providing a range of carcass sire types across the three carcass classes. Matings were by artificial insemination to Hereford dams from a single herd. Steer progeny were grown at conventional (slow: ~0.5 kg/day) or accelerated (fast: ~0.7 kg/day) rates from weaning to feedlot entry weight, targeting group means of 400 kg. Accelerated and conventionally grown groups from successive calvings entered the feedlot at similar entry liveweights at the same time, then having identical management during the 100-day finishing phase before slaughter. Within finishing cohorts, fast backgrounding growth resulted in increased subcutaneous fatness at feedlot entry in steers of all carcass types. Slow growth during backgrounding resulted in faster (compensatory) growth in the feedlot in all classes and sire types. This increased the deposition of fat in slow-backgrounded steers compared with that in fast-backgrounded steers during feedlotting, and thus reduced the difference between the groups in P8 and rib fat at feedlot exit. However, there did appear to be an advantage in the level of compensation in the feedlot in favour of those sire types with a genetic propensity for faster growth. Backgrounding growth rate affected body composition and the rate of weight gain during finishing. Faster growth produced more subcutaneous fat during both backgrounding and finishing. Steer progeny groups clearly showed the expected responses in growth and body composition, on the basis of the genetic potential of their sires.

Metabolic traits affecting growth rates of pre-pubertal calves and their relationship with subsequent survival

This study related growth and metabolic traits in Holstein-Friesian calves (n=45) to subsequent performance and longevity. Animals were measured at birth, 3, 6 and 9 months (weight, crown rump length (CRL), heart girth and height). Endocrine and metabolic traits were assessed at 6 months of age. These traits were not influenced by sire (n=5). Milk production and mortality records were obtained through 3 lactations. Seven heifers failed to achieve a lactation, 6 were culled after one, 17 after two and 15 (33%) survived >/=3 lactations. Birth weight and girth but not skeletal measures were highly positively correlated with the repeated size measurements at 3-9 months. Calves with higher cortisol at 6 months were smaller in weight and girth at 3 months, with reduced 3-6 months skeletal growth. GH secretion was related to height, weight and growth, whereas urea was most strongly related to CRL. Calves not achieving a single lactation had lower IGF-I. Calves with higher glucose or BHB were more likely to be culled after 2 lactations, an effect which was independent of yield. Size and metabolic measurements of growing calves may therefore prove useful in predicting longevity.